An example of a printing apparatus is a digital offset printing apparatus. These presses combine ink-on-paper quality with multi-color printing on a wide range of paper, foil and plastic substrates, i.e. print media. These digital printing presses offer cost-effective short-run printing, on-demand service, and on-the-fly color switching.
A digital offset printing apparatus works by using digitally controlled lasers or LED imaging modules for example, to create a latent image in the charged surface of a photo-imaging cylinder. The lasers are controlled according to digital instructions from a digital image file. Digital instructions can include various parameters, such as image color, image spacing, image intensity, order of the color layers, etc. Ink is then applied to the partially-charged surface of the photo-imaging cylinder, recreating the desired image (or a single color separation of a corresponding color image). The image is then transferred from the photo-imaging cylinder to a heated blanket cylinder, and from the blanket cylinder to the desired substrate, which is placed into contact with the blanket cylinder by means of an impression cylinder.
An operator of a printing apparatus can prepare an ink of a certain color by mixing appropriate quantities of different colored inks. However, such methods of mixing an ink can be messy and require expertise to undertake. Moreover, such ink mixing methods are reliant on the operator's skill in mixing the ink and hence are sensitive to human error.